Purple sweet potato gives this ganache tart delicious flavor and a naturally purple hue. Classic French short crust pastry is the perfect foil for the rich filling.I made this in a 9-inch blossom-shaped tart pan with a removable bottom, but you could use a standard 9-inch pie plate or an 11-inch standard-sized tart pan.
7/8cup14 tablespoons/198g unsalted butter, cold and cubed
1/2cup3.5 oz./100g fine granulated sugar
1 1/2cupsheavy whipping cream
6tablespoonsube or purple sweet potato powder
12oz.three 4oz. bars white chocolate, chopped
Frozen ube ganache stars
Pate sucrée cookies
Organic rose petalsoptional
Place the flour, salt, and sugar in the bowl of a food processor, pulse to combine. Add the cubed butter on top of the flour and pulse repeatedly in short bursts until the mixture looks crumbly. Add the vanilla and egg and pulse until the mixture forms a ball to one side of the bowl. Remove the dough and flatten into a circle. Cover with plastic wrap and let rest 30 minutes before use.
Preheat the oven to 375°F.
Roll the dough on a lightly floured piece of parchment paper using a floured rolling pin to 1/4-inch thickness. Pick up the pastry on the paper and invert it onto the tart pan or pie plate. Peel away the parchment and fit the crust into the pan. Trim away the excess dough. Chill the crust in the pan for 15 minutes.
Fit a piece of parchment on top of the pie crust and add pie weights (I use dry brown rice). Cook for 20-25 minutes, or until the pie is golden around the edges and fragrant. Let cool completely.
Re-roll dough scraps to 1/4-inch thickness and cut out various sizes of flower shapes. Transfer to a parchment-lined baking sheet and bake for 10-12 minutes, or until cookies are golden. Let cool completely.
Heat the cream in a saucepan over medium heat until steaming but not boiling. Add 3 tablespoons of the ube powder; whisk until well combined. In a separate bowl, place the remaining 3 tablespoons of ube powder. Add hot water a little at a time as needed (about 3-4 tablespoons at first, then more to consistency) to form a medium-bodied potato paste. Whisk this mixture into the cream a spoonful at a time. If the mixture looks lumpy, use and immersion blender to combine it thoroughly (or transfer to a blender, but be careful not to turn the heavy cream into whipped cream). While the cream is still hot, add the white chocolate and whisk gently to combine. When a glossy ganache is formed, pour it into the cooled pie crust. You will have leftover ganache. Transfer the pie to the refrigerator to chill 4 hours, or overnight.
Chill the leftover ganache for at least an hour or until the bowl is cool to the touch. Whip the ganache on a standing mixer on high speed until a thick, buttercream-stiff consistency is achieved. This will cause the purple hue to lighten.
Line a baking sheet with parchment. Transfer the whipped ganache to a piping bag fitted with a large open star tip. Pipe large and small stars on the parchment paper and transfer to the freezer to set firmly, about 30 minutes.
When the tart is firmly set, use a small offset spatula to pick up frozen ganache stars from the parchment and transfer to the top edge of the tart. Alternately place cookies, raspberries and rose petals, if using. You can cover one side of the tart with decoration as I did, or completely fill the center of the tart. You should have enough cookies and ganache stars to do so. Serve the tart immediately, or cover and chill until you’re ready to serve. Refrigerate leftovers.